1. Field of the Invention
The present invention relates to liquid crystal display devices, and more particularly to a technique suitable for application to back-side prism type backlights.
2. Description of the Related Art
TFT (Thin Film Transistor) liquid crystal display modules with small color liquid crystal display panels of about 240×320×3 subpixels are widely used as display units in mobile appliances such as cell phones.
Such liquid crystal display modules for cell phones can be improved in brightness by employing back-side prism type backlights.
FIG. 5 provides a cross sectional view of a main portion illustrating the outlined structure of a conventional liquid crystal display module for cell phone, the module using a back-side prism type backlight.
As shown in FIG. 5, the conventional liquid crystal module for cell phone has a liquid crystal display panel and a back-side prism type backlight which illuminates the liquid crystal display panel.
The backlight comprises: a light guide plate 6 having a nearly rectangular shape similar to the plane shape of the liquid display panel; white light emitting diodes 8 disposed at one side surface (incident surface) of the light guide plate 6; a reflection sheet 7 disposed on the bottom surface (opposite to the liquid crystal display panel side) of the light guide plate 6; a back-side prism sheet 5 disposed on the top surface (liquid crystal display panel side) of the light guide plate 6; and a diffusion sheet 4 disposed on the top surface of the back-side prism sheet 5. The back-side prism sheet 5 is a prism sheet having prisms on the side of the light guide plate 6.
The liquid crystal panel has a liquid crystal cell 2, an upper polarization plate 1 attached to the top surface (display surface) of the liquid crystal cell 2 and a lower polarization plate 3 attached to the bottom surface (backlight side) of the liquid crystal cell 2.
The technical documents related to the present invention include:
[Patent Document 1] Japanese Patent Laid-Open No. 2001-166116
[Patent Document 2] Japanese Patent Laid-Open No. 2001-166302